This invention is directed to clay extruders, and more particularly, to a unique and improved lubricating apparatus for clay extruders which improves the life expectancy of the die and lubricating apparatus, as well as improving the penetration of lubricant into the clay material. While the present invention will be described in connection with a brick extruder, it should be recognized that the inventive concept is equally applicable to any type of extruder in which clay, ceramics, or other material is processed and which requires lubrication of the material at or approximately near the entrance to the forming die.
In the extrusion of clay for bricks, the raw clay passes through an extruder casing which is generally round or oval in cross-section. At the exit end of the extruder, the clay is introduced into a forming die which transforms the cross-sectional shape of the clay column into a rectangular bar from which the individual bricks are eventually cut. In the forming die, the plastic moving body or stream of clay or other ceramic material must be gradually diminished in size and shape into a rectangular form that issues forth from the exit end of the die. As a result, a tremendous amount of energy is expended, and considerable friction occurs between the clay and the side walls of the forming die, particularly in the areas which eventually become the corners of the brick. This friction may cause some areas of the clay to move faster or slower than other portions. The use of conventional bridges (for forming holes in the brick) tend to exaggerate this problem. In order to alleviate this problem and ensure that the side and corner portions of the clay move with sufficient ease, speed, and uniform velocity, there have been previously utilized devices, called "oil rings", for applying oil or other suitable lubricants to the surface, and particularly to the corners of the stream of clay. As a result the side and corner portions of the brick are caused to advance with reduced friction and wear, thereby producing better bricks, in that they are smoother and more compact at the edges and corners. See U.S. Pat. Nos. 721,152 to Chambers, Jr. and 1,220,902 to Steele for examples of earlier lubricating devices.
Generally, such lubricating systems are formed in and as part of the forming die. See U.S. Pat. No. 4,174,933 to Mitchell et al. In a relatively recent type of conventional clay extruder, raw clay is moved along a cylindrical barrel by a screw or ram and forced through the forming die which has a circular or oval entrance and a rectangular outlet. The term "cylindrical" includes cross-sections which are either circular or oval shaped. The forming die includes a conduit or passageway therein for the introduction of lubricant. A liner is welded to the inner surface of the die adjacent the entrance thereof and includes one edge (downstream) which has openings therein through which lubricant is allowed to pass into the clay material. As the clay leaves the extruder casing, which generally has a circular or oval opening at the end thereof, it immediately contacts the liner which is tapered inwardly in the same general shape as the die. This results in the clay impinging upon the surface of the liner at a positive angle resulting in rapid wear or deterioration of the liner. When the liner is worn, the entire die must be replaced or refurbished. Unless the brick plant carries an identical spare die, there then results "downtime" which is very expensive. Spare dies are also very expensive.
The lubricant is applied in such conventional apparatuses at a point several inches downstream from the entrance to the die, after the clay has begun to be compacted. As a result it is difficult to obtain good penetration of the lubricant into the compacted surface of the clay.
In order to address these concerns, the present invention first separates the lubricating function from the die by providing a separable lubricating ring interposed between the exit end of the extruder casing and the entrance end of the forming die. In this separable lubricating ring, the functions of receiving lubricant, conducting and storing the lubricant under pressure throughout the lubricating ring, and causing the lubricant to pass therefrom and into the clay are all self-contained within the lubricating ring.
Secondly, the lubricating ring is formed of an annular outer member having a cylindrical inner surface and a frustoconical liner attached at one edge to the inner surface thereof and spring-biased at the downstream edge against the inner surface of the outer member providing a reservoir for the lubricant therebetween. Because of the frustoconical shape, the liner actually presents negative angle of impingement which achieves several surprising results. First of all, the liner is not subject to the rapid wear and deterioration as would occur in a liner having a positive angle of impingement. Because of the frustoconical shape and negative angle of impingement, the clay column actually expands as it passes through the lubricating ring so that the clay loosens and allows better penetration of lubricant thereinto. Finally, when the liner does become worn and must be replaced, only the lubricating ring must be removed and refurbished. Since the lubricating ring does not have a peculiarly machined or formed inner surface and is compatible with substantially all dies, it is much more economical to carry spare lubricating rings than spare dies.
Another feature of the lubricating ring is the provision of spaced dams between the liner and the inner surface of the outer annular member and a plurality of inlet ports for lubricant. So arranged, the lubricating ring can be divided into quadrants, so that a controlled supply of lubricant can be directed to selected areas of the clay column. Some quadrants may receive differing quantities of lubricant from other quadrants. The dams actually divide the reservoir of the lubricating ring into a plurality of separate chambers.
The liner is fabricated as a relatively thin, frustoconical plate having a first and second edge. The first edge, when assembled on said lubricating ring, is positioned at the upstream end thereof adjacent the exit end of the extruder casing. The second edge, when assembled, is positioned adjacent the entrance of the forming die at the downstream end of the lubricating ring. The first edge is formed with a diameter less than the diameter of the inner wall of the annular outer member and the second edge is formed with a diameter slightly greater than the corresponding inner diameter of the inner wall of the annular outer member. So arranged, when the liner is assembled, the first edge is spaced from the inner wall by a rod which extends around the inner wall and secured thereto by welding. The second or downstream edge is then caused to be spring-biased against the inner wall because of the frustoconical shape and diameter thereof. The lubricant, because of the pressure within the reservoir and a plurality of axially extending grooves which extend along the inner wall of the outer member, is caused to exude beneath the second edge into the surface of the clay material passing thereby.
It is therefore an object of the present invention to provide an improved lubricating device for clay or ceramic extruders.
It is another object of the present invention to provide a lubricating device of the type described which includes a separable lubricating ring inserted between the exit end of the extruder casing and the entrance end of the die.
It is yet another object of the present invention to provide a lubricating device of the type described which includes a frustoconical liner affixed to an annular outer member in such a manner as to provide a negative angle of impingement between the clay and the lubricating ring.
It is yet another object of the present invention to provide a replaceable liner for lubricating rings of the type described.